Roussel had 27 points (12 goals, 15 assists) in 60 games and five points (four goals, one assist) in the five games before the injury.
Over the past three-plus seasons, Roussel, 27, missed nine games and played in 80 games or more in each of the past three seasons.
Ruff said the injury will force him to juggle his penalty kill, potentially using forwards Tyler Seguin and Jason Spezza on faceoffs, with Brett Ritchie expected to have an expanded role.
The Stars called up forward Remi Elie from Texas of the American Hockey League on an emergency basis. Elie, 21, a second-round pick (No. 40) in the 2013 NHL Draft, will make his NHL debut against the Florida Panthers on Saturday (7 p.m. ET; FS-F, FS-SW, NHL.TV).
"Good skater, heavy on the puck," Ruff said of Elie. "He plays a lot like [Roussel]. Very determined player on the forecheck, very hard player to play against."
Forward Ales Hemsky didn't practice Friday and is a questionable for Saturday after he blocked a shot by Boychuk with his foot.
"He had further tests this morning, [X-rays] look negative, but there is a little bit of concern whether the swelling will allow him to get his foot in the boot and be able to play," Ruff said. "Tomorrow we'll have that answer."
Hemsky played his first game since Oct. 22 on Thursday. He missed five months after having hip surgery to repair an injury sustained playing for the Czech Republic in the World Cup of Hockey 2016.
If Hemsky can't play, the Stars could use 11 forwards and seven defensemen against the Panthers, Ruff said.
Forward Adam Cracknell, who has missed four games with a lower-body injury, was a full practice participant Friday but won't play Saturday. Ruff said he's hopeful Cracknell will play Monday at the Washington Capitals.
